P21E0
Cylinder 3 Injector B Circuit Low
Cylinder 3 second-injector (B) drive line stuck low — short to ground. A flow-deviating injector throws off cylinder balance — adjacent cylinders run leaner/richer to compensate, often masking the root cause until the trim limit is hit.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Short to groundCommon
- Connector pins corroded - high contact resistanceLess likely
- Harness chafing through insulationLess likely
Parts involved
- Fuel Injector
P21E0 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.